86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
/* @(#)s_nextafter.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/* IEEE functions
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* nexttoward(x,y)
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* return the next machine floating-point number of x in the
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* direction toward y.
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* Special cases:
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*/
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#include <float.h>
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#include <openlibm_math.h>
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#include "math_private.h"
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double
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nexttoward(double x, long double y)
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{
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int32_t hx,ix;
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int64_t hy,iy;
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u_int32_t lx;
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u_int64_t ly;
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EXTRACT_WORDS(hx,lx,x);
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GET_LDOUBLE_WORDS64(hy,ly,y);
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ix = hx&0x7fffffff; /* |x| */
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iy = hy&0x7fffffffffffffffLL; /* |y| */
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if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
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((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0))
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/* y is nan */
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return x+y;
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if((long double) x==y) return y; /* x=y, return y */
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if((ix|lx)==0) { /* x == 0 */
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volatile double u;
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INSERT_WORDS(x,(u_int32_t)((hy>>32)&0x80000000),1);/* return +-minsub */
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u = x;
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u = u * u; /* raise underflow flag */
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return x;
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}
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if(hx>=0) { /* x > 0 */
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if (hy<0||(ix>>20)>(iy>>48)-0x3c00
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|| ((ix>>20)==(iy>>48)-0x3c00
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&& (((((int64_t)hx)<<28)|(lx>>4))>(hy&0x0000ffffffffffffLL)
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|| (((((int64_t)hx)<<28)|(lx>>4))==(hy&0x0000ffffffffffffLL)
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&& (lx&0xf)>(ly>>60))))) { /* x > y, x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x < y, x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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} else { /* x < 0 */
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if (hy>=0||(ix>>20)>(iy>>48)-0x3c00
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|| ((ix>>20)==(iy>>48)-0x3c00
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&& (((((int64_t)hx)<<28)|(lx>>4))>(hy&0x0000ffffffffffffLL)
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|| (((((int64_t)hx)<<28)|(lx>>4))==(hy&0x0000ffffffffffffLL)
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&& (lx&0xf)>(ly>>60))))) { /* x < y, x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x > y, x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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}
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hy = hx&0x7ff00000;
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if(hy>=0x7ff00000) {
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x = x+x; /* overflow */
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return x;
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}
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if(hy<0x00100000) {
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volatile double u = x*x; /* underflow */
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}
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INSERT_WORDS(x,hx,lx);
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return x;
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}
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